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Worldwide glaciers are annually retreating due to global overheating and this phenomenon determines the potential lost of microbial diversity represented by psychrophilic microbial population sharing these peculiar habitats. In this context, yeast strains, all unable to grow above 20°C, consisting of 42 strains from Antarctic soil and 14 strains isolated from Alpine Glacier, were isolated and grouped together based on similar morphological and physiological characteristics. Sequences of the D1/D2 and ITS regions of the ribosomal DNA confirmed the previous analyses and demonstrated that the strains belong to unknown species. Three new species are proposed: Mrakia robertii sp. nov. (type strain CBS 8912), Mrakia blollopis sp. nov. (type strain CBS 8921) and a related anamorphic species Mrakiella niccombsii sp. nov. (type strain CBS 8917). Phylogenetic analysis of the ITS region revealed that the new proposed species were closely related to each other within the Mrakia clade in the order Cystofilobasidiales, class Tremellomycetes. The Mrakia clade now contains 8 sub-clades. Teliospores were observed in all strains except CBS 8918 and for the Mrakiella niccombsii strains. [ABSTRACT FROM AUTHOR]

Yeast, particularly Saccharomyces cerevisiae, has long served as a model eukaryotic system for studies on the regulation of lipid metabolism. We developed a high performance liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry method for the detailed analysis of triacylglycerols (TAGs) in 14 species of yeast consisting of seven Antarctic yeasts (grown at 15°C and 5°C) and seven non-Antarctic yeasts (grown at 25°C and 15°C), the latter including 3 strains of S. cerevisiae. Analysis of TAG molecular species established that the sn-2 position was invariably occupied by an unsaturated fatty acyl moiety. In S. cerevisiae the preference was for oleic acid 18:1>palmitoleic acid 16:1, in Candida albicans, Cryptococcus humicolus and Rhodotorula mucilaginosa 18:1>linoleic acid 18:2 and in Zygosaccharomyces rouxii 18:2>18:1. In the Antarctic yeasts (Cryptococcus watticus, Cryptococcus victoriae, Cryptococcus nyarrowii, Leucosporidium antarcticum, Leucosporidium fellii, Candida psychrophila and Rhodotorula mucilaginosa) the general pattern was for the sn-2 position to be occupied by 18:1, 18:2 or linolenic acid 18:3. A trend towards synthesis of increased unsaturated fatty acid in TAGs was observed as the growth temperature was lowered. The application of principal component analysis demonstrated that the yeasts were differentiated into three distinct groups. One group consisted of the three S. cerevisiae strains, a second the other four non-Antarctic yeasts and the third the seven Antarctic yeasts. The data for the Antarctic yeasts, to the best of our knowledge, have not been previously reported. [ABSTRACT FROM AUTHOR]